Conventional-type drum brakes include an abutment that is fixed or that moves relative to the plate to which a first end of the shoe is fixed, which first end is opposite from a second end in contact with the wheel cylinder, the wheel cylinder transmitting the braking command directly to the shoe which is mounted to pivot relative to the plate at its end fixed to the abutment.
Drum brakes offer several advantages over disk brakes. For the same application force, the braking torque is generally larger in a drum brake than in a disk brake. The “handbrake” function is easier to install on a drum brake than on a disk brake. Therefore, drum brakes are still used, in particular on the back wheels of vehicles.
However, replacing a drum brake shoe when its friction lining is worn requires a relatively long disassembly and reassembly operation to be performed. In addition, the stability of the braking torque could be improved.
Because of the way forces exerted in the drum brake are distributed during braking, the shoe is subjected to a roll-up phenomenon that can reduce the stability of the braking and therefore the stability of the vehicle.
During braking, four forces are remarkable in a drum brake: firstly an inlet force at the contact between the wheel cylinder and the first end of the shoe, secondly an application force at the contact between the lining and the drum, thirdly a braking force at the point of contact between the second end of the shoe and the abutment, and fourthly a reaction force at the point of contact between the second end of the shoe and the abutment. The fact that the braking force and the reaction force are applied at the same point tends to give rise to shoe roll-up.